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It's Thunderstorm Season - Are You Ready For Convective SIGMETs?

Primary Image - Convective SIGMETs Adam Sacco

It's officially thunderstorm season, with severe storms ripping through the entire country over the past several days. What's that mean for you? It's probably time for a quick refresher on Convective SIGMETs.

We know how much you dislike love reading the Aviation Weather Services handbook, so instead, here's a quick review of what types of weather are included in Convective SIGMETs, along with some cool pictures.

You're probably familiar with the fact that Convective SIGMETs contain bad weather, but how bad does it have to be? There are three different weather conditions included in a Convective SIGMET. The first one is:

  • An area of thunderstorms affecting 3,000 square miles or greater, with thunderstorms affecting at least 40% of the area

That's great, but here's the next question: how big is 3,000 square miles? That sounds like a lot, right? It's actually smaller than you may think. Here's a map with 3,000 square miles highlighted in orange. Since only 40% of that area needs to be affected by the storms, it actually ends up being a fairly small area.

Convective SIGMET - 3,000 Square Miles

Next up we have the 2nd and 3rd conditions for Convective SIGMETs:

  • A line of thunderstorms at least 60NM long, with thunderstorms affecting at least 40% of the length
  • Severe or embedded thunderstorms affecting any area that are expected to last 30 minutes or more
These two are a little easier to visualize, but since we're really into maps, here's what a 60NM line of thunderstorms would look like, highlighted in orange. Again, only 40% of the area needs to be affected to be included in the Convective SIGMET.
Convective SIGMET - 60NM Line of Thunderstorms

Special Convective SIGMETs

So what happens when dangerous and localized weather pops up? The National Weather Service issues a special Convective SIGMET. What's in it? Any of these conditions, if they're expected to occur for more than 30 minutes of the valid period:
  • Tornado
  • Hail 3/4 inch or larger
  • Wind gusts 50 knots or greater
  • Indications of rapidly changing weather conditions

So there you have it. The next time you see a Convective SIGMET, you'll know what kinds of weather, and how large of an area, it covers.

Want to learn more about Convective SIGMETs? Try our Aviation Weather Products course, and quickly learn to read reports and forecasts like this:

WSUS31 KKCI 290255
SIGE
CONVECTIVE SIGMET 7E
VALID UNTIL 0455Z
OH KY
FROM 40E CVG-40W HNN-60ENE LOZ-40E IIU-40E CVG
AREA TS MOV FROM 27015KT. TOPS TO FL380.

OUTLOOK VALID 290455-290855
FROM 40W MKG-HNN-SPA-30NNE TLH-CEW-40W MKG
REF WW 111 113.
WST ISSUANCES EXPD. REFER TO THE MOST RECENT ACUS01 KWNS FROM STORM PREDICTION CENTER FOR SYNOPSIS AND METEOROLOGICAL DETAILS.

In easy-to-understand breakdowns like this:

Boldmethod Training - Convective SIGMETs



Colin Cutler

Colin is a Boldmethod co-founder, pilot and graphic artist. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ-200, and has directed development of numerous commercial and military training systems. You can reach him at colin@boldmethod.com.

Images Courtesy:

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